The present invention relates to a wood cutting knife assembly providing improved knife stability, for use in wood processing.
Many kinds of wood cutting apparatus are used for processing logs, lumber, or wood refuse in a wood processing mill. For example, ring slicers, also termed ring flakers or stranders, are generally used for manufacturing particle board, oriented strand board, and fiberboard such as MDF. They convert logs, refuse lumber, chips, or other articles of wood into flakes, wafers or strands for the manufactured board products. Disc chippers are used to produce chips from waste wood, the chips also being used in manufactured wood products. Wood cutting apparatus having conical heads or drum style heads are used to produce squared lumber from logs.
All of these types of apparatus (hereinafter “wood cutting apparatus”) employ removable knives that are exposed to large, highly episodic cutting forces over prolonged periods of time, yet the knives should be easily removable from the apparatus for maintenance, repair or replacement, and must be held in the apparatus in as stable a configuration as possible to produce high quality dimensioned lumber. It has proven difficult to meet all of these requirements.
A significant advance in the art of wood cutting knife assemblies is represented by Carpenter et al., U.S. Pat. No. 4,997,018, disclosing a knife assembly for use with the knife disclosed in Carpenter et al., U.S. Pat. No. 4,850,408. The knife is double-sided, i.e., has dual cutting edges, to provide a second, alternative cutting edge when the first cutting edge becomes worn or damaged. The knife includes a keyway for receiving a mating projection of a counterknife, the knife being clamped between the counterknife and an outer clamping member. The keyway and mating projection index the knife to the cutting apparatus to which the knife assembly is mounted, and positively secure the knife to the cutting apparatus.
More recently, Schmatjen, U.S. Pat. No. 5,819,826 discloses parallel ridges on the knife which straddle the projection of the counterknife. In addition to creating an effective keyway in the knife, the ridges deflect wood chips cut by the knife so as to reduce packing.
Bradstreet Jr. et al., U.S. Pat. No. 5,271,440, discloses a double-sided knife having a serrated surface for mating reception with a complementary serrated surface of, in this case, the outer clamping member. While apparently more difficult to manufacture than the aforementioned Carpenter et al. knife assembly, the assembly of Bradstreet Jr. et al. is like many in the prior art that are provided in recognition of the need to positively index and secure the knife to the cutting apparatus.
A further significant advance in the art of knife assemblies for use in wood cutting apparatus is represented in U.S. patent application Ser. No. 09/918,895 assigned to Key Knife Inc. The knife disclosed therein has deflector ridges on a front side of the knife to receive a mating projection of the counterknife in the manner of Schmatjen, U.S. Pat. No. 5,819,826, along with a recess in a back side of the knife to receive a mating projection from the outer clamping member of the clamping assembly. The counterknife is relieved and formed so that a definite “three-point” contact is made between the assembly and the knife comprising two points on the bottom surface of the knife and one point on the top surface of the knife. The two points of contact on the bottom surface of the knife are spaced as far apart as is practical, and the third point falls between these two points so that the knife is held in a stable configuration. Yet, the knife remains easy to remove from the assembly, and the complementary features provided in the outer clamping member and the knife actually improves the assembly in this regard.
So far as it is known, the prior art has not improved on this concept. However, the present inventors have recognized opportunities for further improving the stability of the knife in a knife assembly for use in wood cutting apparatus.